During the operating sequence, machines that process or handle a product often have machine elements that have to be exchanged depending on the product when the product is changed. Change systems are known for this, e.g., in container processing machines, whereby in these change systems an operator or a servo-device operates the machine element and screws, twist grips or similar attachment elements in such a way that the machine element is localized at the target position in an unambiguous, controlled manner after the exchange. This is time-consuming, however, and arduous for the operator, particularly in machines that contain a multiplicity of machine elements that have to be exchanged. In order to minimise the exchange times, quick-change systems have therefore become known in which the machine element is localized in the target position, e.g., via an energy accumulator by means of a spring force, i.e., the quick-change system automatically sets up the target position.
Such quick-change systems have become the standard in the widest range of machines and, without restriction, particularly in container processing machines, such as, for example, container blow-molding machines, and there especially for localization of exchangeable fitting parts, molding shells, molding bottoms and the like, whereby in these cases cited only by way of example, the target position is snapped into place, coupled, latched or adjusted in a similar manner, for example, assisted by springs.
In the quick-change system known from EP 2 030 759A, for example, a shielding plate, as a fitting part on a holder of a preform product conveyor chain in a heating module, is localized at the target position with a plug-in foot in a bore hole of the holder by means of a pin-shaped securing element being brought by means of a spring force into an engagement position in which a latching element of the securing element acts in combination with a latch depression of the plug-in foot. For the exchange, the securing element is relocated relative to the plug-in foot by means of an external application of force, e.g. linearly, into a release position before the plug-in foot is pulled out and the plug-in foot of a new fitting part is inserted. The securing element, under the spring force, returns to the engagement position and consequently localises the plug-in foot, and consequently the fitting part, at the target position. This quick-change system allows short exchange times, but holds the danger that the operator or an exchange machine has no influence on it or does not receive any feedback indicating either that the machine element has been properly brought to the target position and is localized there and/or that the securing element, under a spring force, has taken on the locking position. If the machine element is not brought into the target position and/or if the securing element is not properly placed into the locking position, then the machine element can loosen from the holder in an uncontrolled manner during the machine's operating sequence, for example, due to vibrations caused by operation, and either cause damage or prevent proper product processing. In a heating module of a container blow-molding machine, a fitting part that loosens can, for example, damage heating devices or cause incorrect heating of a preform product, from which a fault container is then blow-molded. The fitting part can even fall out. The same applies to molding shells or bottom molds of blow molds with a similar quick-change system.
In a packaging processing machine known from WO 2009/103435 A, format-dependent function elements are exchanged when there is a format change and these function elements are positioned at positions along the processing path that have been provided with identifications. Only during the machine's conversion phase does a computer then carry out a comparison of the target and actual positions of the exchanged function elements, and at least the detected deviations are indicated and, for example, corrected by an operator. If a deviation between the target position and the actual position arises after the operating sequence commences, however, this is no longer detected, so that damage can occur.
Similarly, in a container folding machine known from DE 198 03 820 A, each machine element that depends on the pre-cut part is exchanged when there is a change in the pre-cut part and manually brought into the target position. The actual position is measured with measuring devices when there is an exchange. The target position is stored, so that a computer-assisted comparison can be made in order to ensure correct positioning or in order to derive information for the position correction during the machine's exchange phase. However, if deviations between the target position and the actual position arise later in the operating sequence, it is no longer possible to exclude damage reliably.